Floor underlayment



FIG. 1 is a top perspective view of a floor underlayment showing my new design;

FIG. 2 is a bottom, perspective view thereof;

FIG. 3 is a front elevation view thereof;

FIG. 4 is a left side elevation view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a cross-sectional view thereof taken along line 7-7 in FIG. 5;

FIG. 8 is a rear elevation view thereof; and,

FIG. 9 is a right side elevation view thereof. 

CLAIM The ornamental design for a floor underlayment, as shown and described. 